From 0321b3cf258845104ae272c7794be048ddca7b96 Mon Sep 17 00:00:00 2001
From: Sergei Shulepov <s.pepyakin@gmail.com>
Date: Tue, 5 Nov 2024 15:18:02 +0100
Subject: [PATCH] chore: rid of fs2

fs2 was introduced in PR #500, but we actually don't really need that
much from it. This commit removes the extra dependency in favor of doing
the same directly. I think this is pretty-much equivalent to inlining
the code.
---
 Cargo.lock              | 11 -----------
 nomt/Cargo.toml         |  1 -
 nomt/src/store/flock.rs | 11 ++++-------
 nomt/src/sys/unix.rs    | 21 +++++++++++++++++++++
 4 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 3dfdeb5d..0a2613ea 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -418,16 +418,6 @@ version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9fc0510504f03c51ada170672ac806f1f105a88aa97a5281117e1ddc3368e51a"
 
-[[package]]
-name = "fs2"
-version = "0.4.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9564fc758e15025b46aa6643b1b77d047d1a56a1aea6e01002ac0c7026876213"
-dependencies = [
- "libc",
- "winapi",
-]
-
 [[package]]
 name = "funty"
 version = "2.0.0"
@@ -698,7 +688,6 @@ dependencies = [
  "crossbeam",
  "crossbeam-channel",
  "dashmap",
- "fs2",
  "fxhash",
  "hex",
  "hex-literal",
diff --git a/nomt/Cargo.toml b/nomt/Cargo.toml
index f5eef40f..1180d465 100644
--- a/nomt/Cargo.toml
+++ b/nomt/Cargo.toml
@@ -29,7 +29,6 @@ lru = "0.12.3"
 libc = "0.2.155"
 criterion = { version = "0.3", optional = true }
 thread_local = "1.1.8"
-fs2 = "0.4.3"
 cfg-if = "1.0.0"
 
 [target.'cfg(target_os="linux")'.dependencies]
diff --git a/nomt/src/store/flock.rs b/nomt/src/store/flock.rs
index b562fa0c..cbfe7b23 100644
--- a/nomt/src/store/flock.rs
+++ b/nomt/src/store/flock.rs
@@ -5,8 +5,6 @@ use std::{
     path::Path,
 };
 
-use fs2::FileExt as _;
-
 /// Represents a cross-platform advisory lock on a directory.
 pub struct Flock {
     lock_fd: File,
@@ -22,11 +20,10 @@ impl Flock {
             .create(true)
             .open(lock_path)?;
 
-        match lock_fd.try_lock_exclusive() {
+        match crate::sys::unix::try_lock_exclusive(&lock_fd) {
             Ok(_) => Ok(Self { lock_fd }),
-            Err(_) => {
-                let err = fs2::lock_contended_error();
-                anyhow::bail!("Failed to lock directory: {err}");
+            Err(e) => {
+                anyhow::bail!("Failed to lock directory: {e}");
             }
         }
     }
@@ -34,7 +31,7 @@ impl Flock {
 
 impl Drop for Flock {
     fn drop(&mut self) {
-        if let Err(e) = self.lock_fd.unlock() {
+        if let Err(e) = crate::sys::unix::unlock(&self.lock_fd) {
             eprintln!("Failed to unlock directory lock: {e}");
         }
     }
diff --git a/nomt/src/sys/unix.rs b/nomt/src/sys/unix.rs
index d85b218f..fd7c15dd 100644
--- a/nomt/src/sys/unix.rs
+++ b/nomt/src/sys/unix.rs
@@ -1,2 +1,23 @@
 //! Common Unix definitions.
 
+use std::{fs::File, os::fd::AsRawFd as _};
+
+pub fn try_lock_exclusive(file: &File) -> std::io::Result<()> {
+    unsafe {
+        if libc::flock(file.as_raw_fd(), libc::LOCK_EX | libc::LOCK_NB) == -1 {
+            Err(std::io::Error::last_os_error())
+        } else {
+            Ok(())
+        }
+    }
+}
+
+pub fn unlock(file: &File) -> std::io::Result<()> {
+    unsafe {
+        if libc::flock(file.as_raw_fd(), libc::LOCK_UN) == -1 {
+            Err(std::io::Error::last_os_error())
+        } else {
+            Ok(())
+        }
+    }
+}